I second Thhe Big Lebowski. It's funny when watching it straight but the stoner theme really works best If you watch it under the proper cannabis induced mindset. Also, here's a wild card: Barbarella, Queen of the Universe. This one was a super kitschy 60's soft core sex/sci film starring a young and hot Jane Fonda. It's basically a live action cartoon with ridiculous sets and dialogue. You should be really ripped to appreciate this one. It's a one star movie if you don't have the right attitude.